Biomechanics & Energetics Of Trail Vs. Treadmill Running

Trail running, which consists of running uphill and downhill on technical terrain, is a popular recreational and competitive activity. There has yet to be a systematic investigation that explores the energetics and biomechanics when running across realistic trail conditions (uphill/downhill, varying grade, technical terrain). PURPOSE: This study examined the energetics and biomechanics as males and females ran on a technical trail that had uphill and downhill segments of varied grade. Data from the trail run was compared to treadmill running that matched the slope, velocity and duration of each segment of trail. 15 trail runners (8 females, 7 males) ran out and back on a trail that consisted of 4 segments of varying grade (uphill and downhill; 0.2, 1.2, 7.5 and 8.5%). Velocity and duration for each trail segment was determined via global positioning data. Energetic data [VO₂, respiratory exchange ratio (RER), heart rate (HR)] was recorded continuously via a portable metabolic system, and biomechanical data [(Power (P), ground contact time (GCT), vertical oscillation (VOSC), cadence (CAD), leg spring stiffness (LSS), and impact (IMP)] was recorded via a Stryd power meter. Following the trail testing, subjects performed a treadmill test in which the grade, velocity, and duration were matched to each participant’s trail performance. A three-way repeated-measures ANOVA examined the effects of run surface (trail, treadmill), incline (uphill, downhill) and grade (0.2, 1.2, 7.5, 8.5%) on the measured physiological (VO₂, RER, HR) and biomechanical (P, GCT, VOSC, CAD, LSS, IMP) variables. RESULTS: There was a significant surface x grade x incline interaction with the steeper (7.5 and 8.5%) uphill trail segments resulting in the highest VO2, RER, HR, and P. At all uphill and downhill gradients trail running had a significantly greater VO2, RER, HR, and P compared to treadmill running, and was associated with greater variability in biomechanical variables P, GCT, VOSC, CAD and LSS. CONCLUSION: The demands of navigating technical terrain when trail running result in a 12-15% greater energy demand, which is observed in both uphill and downhill and across a variety of gradients. Correspondingly trail running requires a higher mechanical power output and is associated with greater biomechanical variability.